A. Field of the Invention
The present invention relates generally to heat exchange devices and to components therefor, such devices being used in a variety of heat exchange applications including water heaters and boilers, as well as fluid heat rejection devices.
B. Description of the Prior Art
The present invention deals with heat exchange devices generally. A common example of such a device is a water heater or boiler, although as will become apparent, the principles of the invention can also be applied to other heat exchange applications. Water heaters and boilers (referred to collectively as water heaters in the discussion which follows) typically have a water heater tank, often of the vertical tube type which utilizes fire tubes located above a combustion chamber. The typical prior art gas, oil or gas/oil fired water heater featured a non-pressurized, external combustion chamber which was typically located on the bottom exterior of the water heater. Vertical shell or V-shell heat exchangers of the above type are well-known in the industry.
Water heaters of the above type generally provide for the flow of hot gas through a series of tubes mounted in vertical fashion between top and bottom support plates within the water heater tank. The products of combustion from the combustion chamber pass vertically upward through the upward interiors of the vertical tubes and out a flue outlet. Water is circulated into and out of a chamber in the prior art devices located between the tube support plates. The water contacts and circulates about the exterior of the vertical tubes to effect heat transfer to heat the water.
In U.S. Pat. Nos. 4,465,024; 4,545,329 and 4,938,204, water heater designs are shown which feature one or more submergible, pressurized combustion chambers so that all combustion takes place in the water heater tank interior in a chamber surrounded by water. These improved water heater designs featured an externally mounted, forced draft burner unit mounted on the exterior of the closed tank at a tank opening so that the burner nozzle extends in the direction of the combustion chamber for heating the combustion chamber. The resulting designs decrease heat loss and increase the thermal efficiency of the water heater many times over that which was achievable with the prior art tube and plate arrangement.
A variety of heat exchanger designs are also known which feature, e.g., coiled tube heat exchangers. In such designs as the Legend Burkay from A. O. Smith Corporation of Milwaukee, Wis., water flows through the interior of the heat exchanger tubes while hot products of combustion flow over the outside of the heat exchanger. Certain of the prior art designs in which the water flow was through the tube interior featured finned copper tubes in combination with separate baffle elements. Other manufacturers of similar products, besides A.O. Smith Corporation, include Teledyne LARS Corporation, Lochinvar Corporation, RBI Water Heaters, Ray Pak, and Patterson-Kelley Corporation.
The field of the present invention is not limited to water heater and boiler applications, although those type devices provide a convenient setting for explaining the principles of the invention. Other heat exchanger applications for the present invention include fluid heat rejection devices which feature water cooling and air heating, for example.
A need exists for an improved heat exchanger coil design which is simple in design and economical to manufacture and which exhibits improved efficiency over existing designs.
Also, despite the above noted improvements in heat exchanger, water heater and boiler designs, a need has continued to exist for an improved water heater of the finned copper tuber variety which could be produced economically and which would be effective for heating potable water for end use applications, or for heating non-potable water for the purpose of, e.g., transferring heat to an air space or to a process, such as for food or chemical processing or other similar water heater and boiler applications.
A need also exists for improvements in condensing water heater designs featuring heat exchange components of the finned copper tube variety, in which the metallic components are treated for corrosion protection in order to protect them from acidic condensation and other forms of corrosion or contamination which can damage untreated copper or cupronickel materials.